Captive-rearing duration may be more important than environmental enrichment for enhancing turtle head-starting success

Abstract

Raising captive animals past critical mortality stages for eventual release (head-starting) is a common conservation tactic. Counterintuitively, post-release survival can be low. Post-release behavior affecting survival could be influenced by captive-rearing duration and housing conditions. Practitioners have adopted environmental enrichment to promote natural behaviors during head-starting such as raising animals in naturalistic enclosures. Using 32 captive-born turtles (Terrapene carolina), half of which were raised in enriched enclosures, we employed a factorial design to explore how enrichment and rearing duration affected post-release growth, behavior, and survival. Six turtles in each treatment (enriched or unenriched) were head-started for nine months (cohort one). Ten turtles in each treatment were head-started for 21 months (cohort two). At the conclusion of captive-rearing, turtles in cohort two were overall larger than cohort one, but unenriched turtles were generally larger than enriched turtles within each cohort. Once released, enriched turtles grew faster than unenriched turtles in cohort two, but we otherwise found minimal evidence suggesting enrichment affected post-release survival or behavior. Our findings suggest attaining larger body sizes from longer captive-rearing periods to enable greater movement and alleviate susceptibility to predation (the primary cause of death) could be more effective than environmental enrichment alone in chelonian head-starting programs where substantial predation could hinder success.

Coexistence conservation: Reconciling threatened species and invasive predators through adaptive ecological and evolutionary approaches

“…Eastern box turtles (Terrapene carolina) in Michigan, US survived longer if they were head-started (grown in captivity) for longer before reintroduction (Tetzlaff et al, 2019).…”